Adaptation Displacement: While the novel is still considered a hallmark of Hardboiled Detective fiction, the film is a far more widely celebrated classic that continues to be referenced today. Far more people are aware of the film than the novel. Even fewer are aware that the 1941 film wasn't even the first adaptation of the source material, which was previously adapted in 1931 and 1936.
Award Snub: Its failure to win Best Picture for 1941 would be understandable, as it was up against no less a cinematic classic than Citizen Kane... Except that one didn't win either. The real winner, How Green Was My Valley, is still considered one of the biggest flubs in Oscar history.
Kasper Gutman still has his share of modern-day fans for being Affably Evil and charming despite all his ruthless acts, a serious Determinator, and aiming for negotiation and bribery rather than the usual violence. Not to mention being the future inspiration for The Kingpin.
Brigid O'Shaughnessy is pretty much to go to character for a Femme Fatale, she's also shown to be great at manipulation and would have succeeded if our hero wasn't as smart as she was.
Have a Gay Old Time: This is a rare case where the trope is Inverted. The word gunsel was a 1920s homophobic slur for a younger, subservient sex partner to an older man. But The Maltese Falcon movie changed its meaning to 'Hired gun' for several decades afterward.
Heartwarming Moments: Any time Sam Spade's trying to avenge his dead partner, Miles Archer. There's also his speech towards the end about how he had a detective's moral code saying he had to get revenge on the killer when his partner's murdered. Spade wasn't even fond of his partner, but he was still willing to avenge him by any means necessary. Plus, he was in love with Brigid at the time, and he was less than pleased when he realized she out of all people had killed Miles, and he had to turn her into the police, but he did it anyway. Spade may be an Anti-Hero, but this one moment alone shows that Spade is not heartless.
Misanthropic detective Samuel "Sam" Spade is a ruthless operator caught in a web of betrayal, lies and murder by the brilliant criminal Kasper Gutman. Upon being roped into the hunt for the Falcon, Spade manages to outwit his captors, even faking being a foolish hothead to lull them into a sense of security. Later proposing a "fall guy", Spade has the criminals turn on one another and sell Gutman's supposedly beloved friend Wilmer out for the police. Upon being rid of Gutman, Spade works out that his lover Brigid O'Shaughnessy was the murderer of his partner Miles Archer and sees through her attempts to manipulate him, turning her over to the police while informing her not to be so sure he's "as crooked as I'm supposed to be," vowing to wait for her if she's out of jail and to remember her if she's hanged.
Kasper Gutman, the "Fat Man", is the Big Bad and an amiable, corpulent crime lord who has been pursuing the titular black bird for seventeen years without ever stopping. Ruthless to the point of murder but sincerely polite, Gutman opts for negotiation and bribery as opposed to the ineffective, brutish violence of his minions, stating "there are other methods of persuasion asides from killing and threatening to kill," patiently overwhelming the protagonist Sam Spade, drugging him, and remaining unflappably calm even as Spade gains the advantage. Gutman's drive is such that he's even willing to use hitman Wilmer as a fall guy for the murders so he can continue the search for the bird, and when he discovers the Maltese Falcon he receives is a fake, Gutman is shaken for all but a minute before he cheerfully laughs it off and decides to continue onto Istanbul, remaining no less persevering as he has for the previous seventeen years and even offering Spade the chance to come with him on the hunt.
Memetic Mutation: Sam Spade disarming his opponents and occasionally mocking them.
Obvious Judas: We're supposed to be surprised when it turns out Brigid's the one who killed Sam Spade's partner, Miles Archer, but considering how suspicious she was for the majority of the film, and the fact that even Sam himself didn't trust her for those reasons, the twist should have been pretty obvious.
Moral Event Horizon: The Fat Man is jovial and affable enough to constantly make you forget he is a ruthless murderer and criminal. He doesn't quite cross the line onscreen until the climax, where he acquiesces to Sam's fall guy scheme and decides to set up his own loyal goon Wilmer—whom he up to now has regarded as a son—for the cops, with an ice-cold line that plunges the Fat Man over:
"I couldn't be fonder of you if you were my own son. But, well, if you lose a son, it's possible to get another. There's only one Maltese Falcon."
James Berardinelli noted in his review of the film that Bogart's performance as Sam Spade singlehandedly reversed audience expectations for private investigators in movies. Before this movie came out, PIs in films were expected to be independently wealthy, cooperate with police, and avoid getting their hands dirty. Portraying Spade as an abrasive, thuggish, misanthropic Anti-Hero was seen as radical at the time. However, nearly every PI in film noir afterwards was so heavily based on Spade that the character can feel boring and clichéd to modern audiences.
In addition to expectations for PIs, this movie also completely changed the reputation of Humphrey Bogart. Before this movie, Bogart was a B-list actor type-cast as a straightforwardly villainous figure in gangster movies. However, his more complex characters here and in later works like Casablanca have so totally eclipsed all his prior roles in the public's memory that his showing a human side here no longer comes as a surprise.
Strawman Has a Point: Iva Archer, Miles's wife, had a good reason to assume that Sam Spade was the one who killed Miles. He did show some signs of affection towards her like he does with most women in his life and had an affair with her before Miles died.
Joel Cairo, whose effeminate actions were supposed to creep out a 1940s audience but these days it just labels him as an outsider.
The fact that the 1941 film is set during a time when homosexuals were being murdered by the Nazis, and Cairo is clearly a foreigner with an Eastern European accent (plus the fact that he's played by Jewish Peter Lorre, who really did escape the Nazi takeover in 1933) makes him even more sympathetic.
The Woobie: Wilmer, to an extent (he is a hired gun, after all). Hes inexperienced, so Sam repeatedly outdoes him and calls him a homophobic slur, and finally, when Sam argues to make him the Fall Guy, his frustrated, furious reaction borders on Tear Jerker. Made even worse when Cairo and Gutman agree.